Not Applicable
Not Applicable
1. Field of the Invention
This invention relates to an open loop control apparatus for a vacuum controlled system for providing vacuum stability within a predetermine range of vacuum levels and more particularly relates to a vacuum relief regulator for use in a vacuum controlled milking system wherein the vacuum relief regulator includes a transducer for producing output signal which is applied to a control device for producing a control signal for controlling speed of a variable speed motor which drives a vacuum pump at various speeds to maintain enough vacuum reserve to allow efficient vacuum relief operation thereby maintaining the vacuum level of the vacuum system within a predetermined range of vacuum levels.
2. Description of the Prior Art
Vacuumed controlled milking systems are well known in the prior art. Typical vacuum controlled milking are disclosed in U.S. Pat. Nos. 5,141,403; 5,284,180 and 4,011,838.
U.S. Pat. Nos. 5,141,403 and 5,284,180 disclose a low-energy-consuming apparatus and method for controlling vacuum levels in milking machines. The milking machine includes a high vacuum reserve including an adjustable speed drive motor driving a vacuum pump, a low-vacuum reserve which operates the milking appears, and a dual vacuum controller. The dual vacuum controller senses vacuum disturbances in the low-vacuum end and adjusts the flow rate of air from the low-vacuum end to the high vacuum reserve. The high vacuum reserve portion of the apparatus includes a vacuum transducer which senses the vacuum in the high volume reserve which varies in response to the vacuum level in the low-vacuum-reserve, to control the speed of the adjustable speed motor thereby providing a controlled vacuum level with minimum pressure variance and energy savings due to a reduction in demand.
U.S. Pat. No. 4,011,838 discloses a milking machine system which includes a flow rate sensing device, a timing device and a system control means for varying the character of the working and massage vacuums during the milking process. The system uses a conventional vacuum pump and vacuum regulator.
U.S. Pat. Nos. 4,955,408; 4,944,249; 4,273,154; 3,938,547; 3,482,593 and 2,667,856 disclose various vacuum regulator devices which utilize a diaphragm and air ports for controlling vacuum levels in a typical milking system.
U.S. Pat. Nos. 4,191,090; 4,166,476; 3,982,553; 3,583,779 and 3,527,241 disclose various vacuum-pressure regulating devices and pressure regulating devices which utilize a diaphragm for controlling vacuum or pressure levels in a vacuum or pressure system requiring controlled vacuums or pressures. U.S. Pat. No. 4,191,090 discloses the use of an elecro-mechanical transducer located in a vacuum line and separate from a vacuum regulator.
None of the vacuum regulators or systems using vacuum regulators anticipate, disclose, teach or suggest affixing a transducer, such as for example a linear stroke transducer, which produces an output voltage which varies linearly as a function of the displacement of the diaphragm within or inside of the mechanical vacuum controller, to sense the movement of the diaphragm.
In addition, two references which disclose vacuum controlled milking systems having variable or adjustable drive motors for driving a vacuum pump at controlled speeds are: (1) Adjustable Speed Drive for Diary Vacuum Pumps, Pages 1-6 Published by, the EPRI Industrial and Agriculture Business Unitxe2x80x94No. 2, 1996 (the xe2x80x9cEPRI Referencexe2x80x9d); and (2) Smart Technology for Vacuum Pump Control Saves Money and Reduces Noise; Sales Brochure, Sides 1 and 2, Dltech, Inc., 1997 (the xe2x80x9cDLtech Referencexe2x80x9d). The EPRI Reference appears to disclose the same information subject of U.S. Pat. Nos. 5,141,403 and 5,285,180 discussed above.
The Dltech Reference discloses use of a sensing system which functions as a vacuum control in a milking system by controlling the speed of a variable speed frequency motor which drives a vacuum pump. The vacuum control senses vacuum levels in the vacuum system and in components of the milking system, excluding the vacuum regulator. The vacuum control increases or decreases the speed of the variable speed motor as required to increase or decrease the vacuum level. The sensing system detects the attaching of milking units to the milking system and causes the motor speed to increase increasing the vacuum level to match airflow. The sensing system detects completion of attaching of milking units to the milking system and reduces the speed of the motor decreasing the vacuum level.
FIG. 1, labeled Prior Art, depicts a known vacuum controlled system using a milk claw. In FIG. 1, a vacuum source shown by dashed box 20 produces a controlled vacuum by means of a motor 22 driving a vacuum pump 24 at a constant speed. The vacuum is maintained by state-of-the art vacuum regulator 28 which admits or bleeds air at atmospheric pressure into the vacuum system to correct and/or maintain the vacuum level. The vacuum regulator 28 is typically a vacuum controller which is used to mechanically regulate the vacuum levels, an example of which is the vacuum controller disclosed in U.S. Pat. No. 3,938,547.
The vacuum source 20 is used to provide a regulated vacuum to a milking system shown generally as 30. A typical milking system includes a vacuum reservoir 32, milking claws 34, having pulse controlled inflations 38, pulsator 40, appropriate vacuum control lines, milking lines and a collection vessel such as a milk jar 44. Such vacuum controlled milking systems are well known in the art and need not be described in detail herein.
FIG. 2 labeled Prior Art illustrates a known prior art apparatus for use as the vacuum source in lieu of the vacuum source 20 shown in FIG. 1. This vacuum source is likewise illustrated by dashed box 20 in FIG. 2. In FIG. 2, a vacuum pump 50 is driven by a three phase AC variable speed motor 52, the rotational speed of which is controlled by a variable frequency drive 56. In the prior art apparatus, a control device 60 is responsive to a vacuum transducer 64 which detects the absolute vacuum level and sends a signal representative of the absolute vacuum level to the control device 60 which is responsive thereto to vary the speed of the motor. A vacuum controller 68 is used to mechanically regulate the vacuum level.
The present invention relates to an improved vacuum controller for regulating the vacuum level and to a transducer which is adapted to be operatively connected to the vacuum controller for providing an output signal which represents an instantaneous position of the diaphragm, a valve and valve opening in the vacuum controller. The output signal is used to generate or produce, as the case may be, a control signal to control the speed of the AC variable speed motor driving the vacuum pump. In the Prior Art apparatus as illustrated in FIG. 2, the signal may be used to control the speed of the variable drive motor.
The present invention discloses and teaches a new, novel and unique open loop control apparatus for a vacuum controlled system for providing vacuum stability within a predetermined range of vacuum levels. The control apparatus includes a vacuum regulator having a diaphragm including a valve member having a valve opening or input port which changes position as a function of the vacuum level within the vacuum system for controllably admitting or bleeding air into the vacuum system to adjust the vacuum level within the system. A transducer is operatively coupled to the diaphragm for producing an output signal which represents the instantaneous position of any one of the diaphragm, valve member, the valve opening or input port. A control device having a pair of inputs and an output, has applied to one of the pair of inputs a set point signal representing a programmed vacuum level for the system. Applied to the other of the pair of inputs of the control device is the output signal from the transducer representing the instantaneous position of the diaphragm. The control device produces, as its output signal, a control signal for controlling speed of a variable speed motor which drives a vacuum pump at various speed as required to enable the vacuum pump to maintain the vacuum level of the vacuum system within a predetermined range of vacuum levels.
A vacuum controller, as disclosed and described in U.S. Pat. No. 3,938,547, is used to mechanically regulate the vacuum level of a milking system by controlling the admission of or bleeding of air into the vacuum system. The vacuum controller includes a diaphragm assembly which mechanically controls the vacuum level through exhausting and in taking air through radial air ports and input ports with a valve member operatively connected to and moveable with the diaphragm. The mechanical resonance characteristics of the diaphragm assembly and related elements provide some mechanical damping such that relatively slow, but acceptable regulation, is achieved which controls the vacuum level in the milking system over a bandwidth of about 3 to 4 inches of Hg.
The present invention discloses a new, novel and unique open loop control apparatus for a vacuum controlled system for providing vacuum stability within a predetermine range of vacuum levels. The open loop control apparatus includes a vacuum regulator having a diaphragm including a valve member having a valve opening which changes position as a function of the vacuum level within the vacuum system for controllably admitting or bleeding air into the vacuum system to adjust the vacuum level within the vacuum system. A transducer is operatively coupled to the diaphragm for producing an output signal which represents an instantaneous position of the valve opening. A control device having a pair of inputs and an output has applied to one of the pair of inputs a set point signal representing a programmed vacuum level for the vacuum system. Applied to the other of the pair of inputs is the output signal from the transducer representing an instantaneous position of the valve opening or input port. The control device produces or generates, on its output, a control signal for controlling speed of a variable speed motor which drives a vacuum pump at various speed to enable the vacuum pump to maintain the vacuum level of the vacuum system within a predetermined range of vacuum levels.
In the preferred embodiment of the present invention, the open loop control apparatus includes a transducer which is directly coupled to and moveable with the diaphragm of a vacuum controller. The transducer is, preferably, a linear stroke transducer which produces an analog voltage signal to represent the position of the diaphragm, valve, valve opening or input port. In the alternative, the transducer may produce a digital voltage signal as its output signal.
The known prior art vacuum controllers provide sufficient regulation of the vacuum levels with a range of 3 inches of Hg to 4 inches of Hg. However, as milking systems and milking claw performances are improved, the regulation of vacuum levels over a smaller range of fluctuations and vacuum levels becomes more important. Regulations of vacuum levels over a range of 0.5 inches of Hg to about 1.5 inches of Hg are now becoming the state-of-the-art. The state-of-the-art vacuum controllers cannot achieve this level of regulation of vacuum levels.
None of the known prior art anticipate, disclose, teach or suggest a vacuum regulator having a transducer or a linear stroke transducer operatively coupled thereto which produces an output signal which is used as an input to an open loop control system for a vacuum controlled milking system.
Therefore, one advantage of the open loop control system of the present invention is that the present vacuum controllers used in a vacuum controlled vacuum system can be adapted with a vacuum control apparatus for providing vacuum stability within a predetermined range of vacuum levels.
Another advantage of the present invention is that the vacuum controller provides energy conservation capability for a diary vacuum system by producing an output signal which is used to vary the speed of the vacuum pump to control vacuum levels while still continuing to maintain the existing precise vacuum regulation.
Another advantage of the present invention is that the open loop control can be used in a vacuum regulator having a diaphragm and valve member which changes position as a function of the vacuum level within the vacuum system for controllably admitting or bleeding air into the vacuum system to adjust the vacuum level within the vacuum system.
Another advantage is that the open loop control of the present invention can use a transducer operatively coupled to the diaphragm of a vacuum regulator for producing an output signal which represents an instantaneous position of the valve opening.
Another advantage is that the open loop control of the present invention can use an electronic simulator to simulate or represent the mechanical operation of a diaphragm of a vacuum regulator for producing an output signal which represents an instantaneous position of the simulated diaphragm and associated valve opening.
Another advantage is that the open loop control of the present invention can utilize a control circuit, which in the preferred embodiment is a comparator or electrical summing junction, having a pair of inputs and an output. One signal applied to one of the pair of inputs is a set point signal representing a programmed vacuum level for the vacuum system and the other signal applied to the other of the pair of inputs is the output signal from the transducer representing an instantaneous position of the valve opening. The output produced by the control device, such as the comparator or electrical summing junction, is used as a control signal for controlling speed of a variable speed AC motor which drives a vacuum pump at various speeds to enable the vacuum pump to maintain the vacuum level of the vacuum system within a predetermined range of vacuum levels.
Another advantage is that the open loop control of the present invention can utilize a transducer directly coupled to and moveable with the diaphragm. The transducer may be a linear stroke transducer which produces an analog voltage signal to represent the position of the diaphragm. The transducer may also be a low voltage digital transducer (xe2x80x9cLVDTxe2x80x9d).
Another advantage is that the open loop control of the present invention can utilize a transducer which produces a digital signal as the output signal.